From the Department of Physiology. Faculty of Medicine. Tabriz University of Medical Sciences. Tabriz. I.R, Iran

Abstract: (1860 Views)

Some large vessels have a mixed functional population of postjunctional α1-
and α 2-adrenoceptors. The purpose of the work presented here was to investigate
the population of postjunctional α -adrenoceptors in the rat isolated common carotid
artelY Male Wi star rats were killed by overdose with pentobarbitone sodium,
after which the left and right common carotid arteries were removed. Rings
of arteries 3-4 mm in length were cut from each vessel and then mounted in 10
mL isolated organ bath, bathed in Krebs maintained at 37°C and gassed with 95%
O2 plus 5% CO2, The preparations were allowed to equilibrate for an hour. When
antagonists were used, the preparations were incubated for at least 45 minutes
with the drugs prior to the onset of a second CCRC. The cunent study focused on
the possibility of post junctional α 2-adrenoceptors that could influence adrenergic
system-mediated vascular α -adrenoceptor responsiveness in this cephalic artery.
The dominance of α 1-adrenoceptors is shown by the high sensitivity of noradrenaline
or phenylephrine to prazosin and the ineffectiveness of rauwolscine, except
in non-selective concentrations. UK-14304 produced contractions and it is
theoretically possible that UK-14304 exerts its actions through combined al and
α 2 activation, but the effectiveness of prazosin and the ineffectiveness of
rauwolscine, except in non-selective concentrations, shows that even this effect is
mediated through α1-adrenoceptors. Thus we suggest that the population of
postjunctional α -adrenoceptors mediating contraction of smooth muscle in the
rat carotid artery is predominantly of the α1type.